High Quality 10 bearings Chrome Steel Ball Bearings, this is a popular size that could be used in many application that uses this size 1.5 x 4 x 2. Bearings are made of Chrome Steel and can rotate up to 115,000 rpm, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination, also bearings are pre-lubricated with grease, Bearings are packed 10 bearings in one plastic tube.